Static mixer and a process for producing dispersions in particular dispersions of liquid fuel with water

Abstract

A static mixer ( 1 )to emulsify water and/or other additives in gas oil comprises a hollow structure ( 2 ) within which two mixing units ( 23,27 ) are disposed, each comprising a first and a second mixing bodies ( 24, 25, 28, 29 ) each carrying a frusto-conical boundary surface ( 24 a , 25 a , 28 a , 29 a ). The boundary surfaces ( 24 a , 25 a , 28 a , 29 a ) are disposed mutually opposite in parallel and facing each other so as to define a narrow mixing gap ( 26, 30 ) of truncated conical form at which the mixture runs in a condition of substantially laminar flow and is submitted to shear forces causing emulsification. Also proposed is a process for producing a dispersion, which process can be carried out by said mixer ( 1 ).

1 . A static mixer comprising: 
 at least one hollow structure ( 2 ) having at least one inlet opening ( 6 ) adapted to be hydraulically connected to a fluid feeding duct ( 3 ) and at least one outlet opening ( 17   a ) adapted to be hydraulically connected to a fluid delivery duct ( 20 );    at least one mixing unit ( 23 ) disposed internally of said hollow structure ( 2 );    characterized in that said at least one mixing unit ( 23 ) comprises a first mixing body ( 24 ) and a second mixing body ( 25 ) having at least a first boundary surface ( 24   a ) and at least a second boundary surface ( 25   a ) respectively, which are opposite to each other and substantially parallel, and positioned to a predetermined distance from each other so as to define at least one mixing gap ( 26 ) through which said fluid flows and is submitted to shear forces.    
     
     
         2 . A static mixer as claimed in  claim 1 , wherein the mixing gap ( 26 ) is substantially devoid of sharp corners so that the fluid is given a condition of substantially laminar flow.  
     
     
         3 . A static mixer as claimed in anyone of the preceding claims, wherein at least one of the first and second mixing bodies ( 24 ,  25 ) is movable to enable the distance between the boundary surfaces ( 24   a ,  25   a ) to be modified.  
     
     
         4 . A static mixer as claimed in anyone of the preceding claims, wherein said mixing gap ( 26 ) has a length corresponding to the length of the generatrix of each boundary surface ( 24   a ,  25   a ) and is of such a nature that the ratio between the length of said mixing gap ( 26 ) and the distance between the boundary surfaces ( 24   a ,  25   a ) is at least as high as 10.  
     
     
         5 . A static mixer as claimed in  claim 4 , wherein the ratio between the length of said mixing gap ( 26 ) and the distance between the boundary surfaces ( 24   a ,  25   a ) has a value included between 15 and 50.  
     
     
         6 . A static mixer as claimed in anyone of the preceding claims, wherein the distance between said boundary surfaces ( 24   a ,  25   a ) is lower than 2 mm.  
     
     
         7 . A static mixer as claimed in  claim 6 , wherein the distance between said boundary surfaces ( 24   a ,  25   a ) is included between 0.2 and 0.5 mm.  
     
     
         8 . A static mixer as claimed in anyone of the preceding claims, wherein the boundary surfaces ( 24   a ,  25   a ) of the mixing gap ( 26 ) are substantially frusto-conical.  
     
     
         9 . A static mixer as claimed in  claim 8 , wherein said boundary surfaces ( 24   a ,  25   a ) have a common axis (“X”) and converge in the opposite direction relative to the inlet opening ( 6 ).  
     
     
         10 . A static mixer as claimed in anyone of the preceding claims; further comprising at least one auxiliary mixing unit ( 27 ) disposed internally of said hollow structure ( 2 ) and having a first auxiliary mixing body ( 28 ) and a second auxiliary mixing body ( 29 ) fitted in said first auxiliary mixing body ( 28 ), said first and second auxiliary mixing bodies ( 28 ,  29 ) having at least a first auxiliary boundary surface ( 28   a ) and at least a second auxiliary boundary surface ( 29   a ) respectively, which are opposite to each other and substantially parallel, and positioned to a predetermined distance from each other so as to define at least one auxiliary mixing gap ( 30 ) through which said fluid flows and is submitted to shear forces.  
     
     
         11 . A static mixer as claimed in  claim 10 , wherein at least one of said first and second auxiliary mixing bodies ( 28 ,  29 ) is movable to enable the distance between the auxiliary boundary surfaces ( 28   a ,  29   a ) to be modified.  
     
     
         12 . A static mixer as claimed in  claim 10  or  11 , wherein the auxiliary boundary surfaces ( 28   a ,  29   a ) of the auxiliary mixing gap ( 30 ) are substantially frusto-conical.  
     
     
         13 . A static mixer as claimed in  claim 12 , wherein said auxiliary boundary surfaces ( 28   a ,  29   a ) have a common axis (“X”) and converge in the opposite direction relative to the outlet opening ( 17   a ).  
     
     
         14 . A static mixer as claimed in anyone of the preceding claims, wherein said hollow structure ( 2 ) comprises: 
 at least one substantially tubular fixed portion ( 9 );    at least one substantially tubular movable portion ( 11 );    first sliding-coupling devices ( 12 ) operatively interposed between said fixed ( 9 ) and movable ( 11 ) portions to give rise to a movable engagement of said portions between a first position in which the boundary surfaces ( 24   a ,  25   a ) are disposed to a minimum preestablished distance and a second position in which the boundary surfaces ( 24   a ,  25   a ) are disposed to a maximum preestablished distance.    
     
     
         15 . A static mixer as claimed in  claim 14 , wherein said first mixing body ( 24 ) is associated with said fixed portion ( 11 ) and said second mixing body ( 25 ) is associated with said movable portion ( 9 ).  
     
     
         16 . A static mixer as claimed in  claim 14  or  15 , wherein said first sliding-coupling devices ( 12 ) comprise: 
 a first screw thread formed on said fixed portion ( 9 );  
 a second screw thread formed on said movable portion ( 11 ), said first and second threads being mutually engaged by screwing.  
 
     
     
         17 . A static mixer as claimed in anyone of  claims 10  to  16 , wherein said hollow structure ( 2 ) further comprises: 
 at least one substantially tubular auxiliary fixed portion ( 17 );  
 at least one substantially tubular auxiliary movable portion ( 14 );  
 second sliding-coupling devices ( 15 ) operatively interposed between said auxiliary movable portion ( 14 ) and said movable portion ( 11 );  
 third sliding-coupling devices ( 18 ) operatively interposed between said auxiliary movable portion ( 14 ) and said auxiliary fixed portion ( 17 ), said first, second and third sliding-coupling devices ( 12 ,  15 ,  18 ) mutually interacting in such a manner that when said fixed and movable portions ( 9 ,  11 ) are in the first position, said auxiliary boundary surfaces ( 28   a ,  29   a ) of said auxiliary mixing bodies ( 28 ,  29 ) are disposed to a minimum preestablished distance and, vice versa, when the fixed and movable portions ( 9 ,  11 ) are in the second position, the auxiliary boundary surfaces ( 28   a ,  29   a ) are disposed to a maximum preestablished distance.  
 
     
     
         18 . A static mixer as claimed in  claim 17 , wherein said first auxiliary mixing body ( 28 ) is associated with said movable portion ( 11 ) and said second auxiliary mixing body ( 29 ) is associated with said auxiliary movable portion ( 14 ).  
     
     
         19 . A static mixer as claimed in anyone of  claims 10  to  18 , further comprising: 
 at least one cogwheel ( 31   a ) fitted on said movable portion ( 11 );  
 at least one shaft ( 31   c ) operatively associated with said cogwheel ( 31   a ) by at least one pinion gear ( 31   b ) associated with the shaft;  
 at least one drive crank ( 31   d ) rigidly in engagement with an end of said gear shaft ( 31   c ).  
 
     
     
         20 . A process for producing a dispersion of at least one primary fluid with at least one secondary fluid, said fluids being substantially immiscible with each other, comprising the step of causing passage of a mixture of said primary fluid and secondary fluid along at least one mixing gap ( 26 ) defined by at least a first boundary surface ( 24   a ) and at least a second boundary surface ( 25   a ) which are opposite to each other and substantially parallel, and positioned to a predetermined distance from each other so as to submit said mixture to shear forces.  
     
     
         21 . A process as claimed in  claim 20 , wherein said mixture is caused to pass along the mixing gap in a condition of substantially laminar flow.  
     
     
         22 . A process as claimed in  claim 20 , carried out by a static mixer as claimed in anyone of  claims 1  to  19 .  
     
     
         23 . A process as claimed in  claim 20 , wherein the primary fluid comprises a liquid fuel and the secondary fluid comprises water.  
     
     
         24 . A process as claimed in  claim 23 , wherein the liquid fuel comprises at least one liquid hydrocarbon of a viscosity at 40° C. from 1 to 53 cSt and a density at 15° C. from 0.75 to 1.1 kg/dm 3 .  
     
     
         25 . A process for production and combustion of a dispersion between a liquid fuel and water, comprising: 
 producing the dispersion between the liquid fuel and water;    feeding said dispersion to a device for combustion of the dispersion;    carrying out combustion of the dispersion; wherein the dispersion is produced according to anyone of claims from  20  to  24 .    
     
     
         26 . A process as claimed in  claim 25 , wherein the dispersion thus produced is directly fed to the device for combustion of the dispersion.  
     
     
         27 . A process as claimed in  claim 25 , wherein the dispersion thus produced is first sent to a storage tank and then fed to the device for combustion of the dispersion.  
     
     
         28 . A process as claimed in anyone of claims from  20  to  27 , wherein the device for combustion of the dispersion is an internal-combustion engine.  
     
     
         29 . A process as claimed in anyone of claims from  20  to  27 , wherein the device for combustion of the dispersion is a burner.